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Old 4th June 2003, 11:14 AM   #21
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Hey sam,

Nice to hear that! Well, I am currently tweaking that clipping detector from Mr Leach and see if it works for my amp. I am also planning to build a Leach amp, not the Super Leach so maybe I can use that LED to detect clipping.

Cheers,
Jojo
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Old 4th June 2003, 03:18 PM   #22
sam9 is offline sam9  United States
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In general cip detectors seem to work by comparring the rail voltage (fixed) to the output peak. When the difference gets below some point say 5V, it "turns on" a cheap opamp which lights the led. The 5V or whatever is set either by a voltage divider or a zener diode. It is chossen to be the point at which an oscilliscope trace first starts to show clipping in the wave form.

What is more interesting is that there will be significant distortion ocurring even before clipping occurs. Rod Elliots's SIM (sound.au.co) which you can access and use detects this before clipping occurs. Until I started playing around with a SPICE program, the degree of this phenomon wasn't so clear. It teaches one to beware of specs like:" <..001% THD+N @1kHz, 1 Watt output" The peaks, though not clipping could be distorying right off the scale.
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Old 4th June 2003, 03:29 PM   #23
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how about (don't know the right name for this)
carver's nulling cct for amp testing?
anytime you have a difference between input and output?
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Old 5th June 2003, 05:33 AM   #24
sam9 is offline sam9  United States
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"how about (don't know the right name for this)
carver's nulling cct for amp testing?
anytime you have a difference between input and output?"


That's pretty much what Rod Elliot's SIM does. His P3A even hat pins to take these. Namely one pin at the base of the transitor that recieves the input signal and the other pin at the base of the transifor that gets the NFB. (I.e, the two inputs of the differential amp.)

The SIM itself is off-board, consisting four opamps (or one quad) and a few passives. Basicly it subtracts one signal from the other and the rsidual is amplified and used to turn on an LED.

All this is explained in more detail on sound.au.com
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Old 8th June 2003, 03:41 PM   #25
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Exclamation Early patents

Quote:
Originally posted by sam9


The SIM itself is off-board, consisting four opamps (or one quad) and a few passives. Basicly it subtracts one signal from the other and the rsidual is amplified and used to turn on an LED.

It's not his idea. Go and check patents 4,048,573 by McIntosh (Power Guard), 4,318,053 by Peavey (DDT) and 5,430,409 by Delco.

http://www.uspto.gov/patft/index.html

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